The present invention relates to a knapsack with a particular structure for bearing against the back to provide the user with better comfort and the knapsack with better stability.
A knapsack comprises a bag and carrier means including shoulder straps and a belt. When the knapsack is in use, it is the posterior face of the bag, referred to herein as the xe2x80x9cbackxe2x80x9d of the bag, which comes into contact with the back of the user. The shoulder straps are fixed to the top of the back of the knapsack either directly to the material constituting said back or optionally to a central device enabling the height of said straps to be adjusted, as described in document FR 2 668 345.
The weight of the knapsack is supported in part by the zone where the straps bear against the shoulders, and special means are implemented for distributing load via the belt. Although it is possible to provide padding between the shoulder strap and the shoulder, the Applicant finds that does not provide the user with a desirable amount of comfort.
Proposals have already been made in document EP 0 122 764 to improve back comfort by fitting the knapsack with shoulder-blade pads which are longitudinal sleeves filled with padding and slidably mounted on two vertical rods which form the stiffening structure of the knapsack. The shoulder straps connect the two shoulder-blade pads to the bag.
The knapsack of document EP 0 122 764 does indeed improve user comfort to some extent, however it requires a special knapsack-stiffening structure with two vertical rods.
The object of the present invention is to provide comfort that is further improved without requiring such a knapsack-stiffening structure.
This object is fully achieved by the knapsack of the invention which comprises, in the manner disclosed in document EP 0 122 764, a bag, two shoulder-blade pads, and two shoulder straps connecting the two shoulder-blade pads to the bag.
In characteristic manner, it comprises:
a) by a one-piece shoulder-blade pad element comprising a reinforcing plate having a central zone and two side zones extending the sides of the central zone symmetrically about the midplane of the knapsack;
b) in that the shoulder-blade pads are disposed in the two side zones on the reinforcing plate and are shaped to bear against the shoulder blades of the user; and
c) in that the reinforcing plate is secured to the back of the knapsack solely via the central zone in the top middle portion of the back.
Thus, by means of the special configuration of the invention, when the knapsack is in use, it is supported near the top of the back not only via the shoulder straps themselves, but also via two shoulder-blade pads, with the load being distributed uniformly over the two shoulder blades by means of the reinforcing plate, even though the knapsack is secured solely via the central zone.
In a preferred embodiment, the connection between the one-piece shoulder-blade pad element and the knapsack is provided with the ability to allow the one-piece element to pivot to a certain extent relative to said back about an axis perpendicular to said back. This ability to pivot provides a degree of independence between the natural movements of the user""s body and those of the bag.
In a variant where the back of the knapsack is made of a flexible material, the central zone of the one-piece shoulder pad element (including its reinforcing plate) is entirely secured to said material, e.g. by stitches, or by self-gripping mechanical attachment elements of the hook-and-loop type, with the ability to pivot being obtained by the ability of said material to deform about the connection zone. Under such circumstances, the back of the knapsack preferably includes at least one stiffening element at a short distance above the connection zone. By means of this stiffening element, which can be located at a distance d of about 1 centimeter (cm) for example, the angular extent of the pivoting is limited. This stiffening element can consist in particular in a strap sewn transversely to the cloth constituting the back of the knapsack, said strap serving as a connection point for a handle for taking hold of the knapsack.
In order to further improve application of the two shoulder-blade pads against the user""s shoulder blades, the reinforcing plate is slightly curved so that the side zones are spaced a little apart from the back of the knapsack when in use, thereby allowing for a certain amount of air flow. When the knapsack is full it is generally of a bulging shape which is curved in the opposite direction to the natural curvature of user""s back. The particular configuration of the one-piece shoulder-blade pad element conforms completely with these differences of curvature.
In an embodiment, the reinforcing plate is made of a material that is rigid or semi-rigid, e.g. a high density foam which is covered in the two side zones by an aerated and damping material constituting the padding of the shoulder-blade pads, e.g. a superposition of a medium density foam and a porous foam that allows air to flow.